The present embodiments relate to a rotating anode having a microstructure on a surface of a focal track.
A focal track containing, for example, tungsten is subjected to high levels of thermal stress while X-radiation is being produced for medical applications by a rotating anode. Temperatures of over 2,500° C. may be reached on the focal track during the creation of X-radiation (where high-energy electrons are slowed down by the focal track, and the X-radiation is produced by bremsstrahlung (“braking radiation”)). The high temperatures may cause premature aging of the focal track. Focal tracks that have undergone aging exhibit substantial cracking and exaggerated grain growth due to recrystallizing of the tungsten structure, with an X-radiation dose rate decreasing as cracking increases. Cracking may be explained by high levels of cyclic temperature stress (e.g., in the case of a rotating anode having typical frequencies of between 100 and 200 Hz) causing the recrystallized tungsten structure to shatter when subjected to fast sequences of tensile and compressive stress. The tungsten structure may shatter to the extent that even whole grains or regions drop out of the focal track, which further reduces the dose rate. The rotating anode will then have to undergo maintenance.
To extend the life of tungsten focal tracks, oxide dispersed strengthening (ODS) or vacuum plasma spraying (VAS) methods that alter the microstructure of tungsten positively may be used.
U.S. Pat. No. 7,356,122 describes an X-ray anode having a thermally-compliant focal-track region for impingement of electrons from an X-ray cathode for producing X-radiation. The thermally-compliant focal-track region has a surface structure of discrete elevations and depressions. The elevations have dimensions of 50 micrometers to 500 micrometers. The depressions have a depth of 10 micrometers to 20 micrometers and a width of 3 micrometers to 20 micrometers.
DE 103 60 018 A1 discloses an X-ray anode having a highly thermally stressable surface with defined microslits being arranged in the relevant surface. The microslits are produced by removing material using a laser beam or high-pressure water jet. An angle of the jet or beam direction is varied relative to a slit base for widening the microslit.